This invention relates generally to a machine for creating compost from waste material, such as manure and biodegradable garbage, and more particularly, to a control system for automating the operation of the rotary composter for the biological degradation of organic waste materials.
Rotary composters are well known in the art, as is represented by U.S. Pat. No. 5,407,809, issued to Larry J. Finn on Apr. 18, 1995. The process achieves an accelerated biological degradation of the waste material to create compost therefrom. While any biodegradable material can be digested within the rotary composter, farm wastes, such as animal manure, are of particular interests because of the desire to fix the nitrogen within the material to prevent stream pollution when the composted waste is spread onto the ground.
Present day manure handling techniques typically provide for a collection of the manure until weather and ground conditions are acceptable to permit the raw manure to be spread over the fields. Since the nitrogen within the raw manure has not been fixed, any runoff, such as would occur following a storm, would have the potential for polluting the streams. Furthermore, free nitrogen in the form of nitrates can leach into the ground water supply and cause pollution. Accordingly, nonpoint sources of pollution, such as farming operations, have come under scrutiny with respect to manure handling.
The biggest problem with known rotary composters has been effective operation. The vessel is preferably sized to process the waste material within approximately three days. While the loading of waste material into the infeed end of the apparatus may be substantially continuous, actually on a periodic basis during the day, compost could be discharged in the same manner. Accordingly, the vessel must be designed to retard material flow through the vessel so that the material can be retained for at least three days. An adequate air supply must be provided through the vessel, as the biological degradation process is aerobic in nature, and the vessel must be designed to maintain a temperature of approximately 120 to 160 degrees fahrenheit, even in cold weather operation.
Efficient operation of the rotary composter is a function of controlling the air flow and rotational speed of the vessel to maintain the proper temperatures within the vessel, as well as the proper levels of carbon dioxide and ammonia gases emanating from the vessel from the composting process. Accordingly, it would be desirable to provide a monitoring system that will sense the temperature and desired gas parameters of the composting process to provide an indication of adjustments that should be made to the volume of air flow through the vessel or the rotational speed thereof. It would also be desirable to provide a control system for automating the operation of a variable flow air infeed mechanism and a variable speed rotational drive mechanism in response to the temperature and gas levels sensed from the composting operation within the vessel.